Impact wrench



May 30, 1939. FTA. .nMERsoN ET AL 2,160,150

` IMPACT WRENCH Filed Oct. 2l, 1957 THEAR ATTORNEY,

Patented .May 30, 1939 IMPACT WRENCH Fronois A. .limer-son and Hoo-olac. Reynolds,

Athens, Pa., assignors to Ingersoll-Rand Company, Jersey City, N. J.,

Jersey a corporation of New Applioation ootobor 2.1, 1937', serial No.110,213

z claims. (cl. 1Qz.3o.5)

impact blows to the tool in order that the tool` may overcome the workresistance.

Devices of this type are usually provided with an anvil member adaptedto4 engage the work and a hammer member through which the driving forceof the motor is transmitted to the anvil. The connecting means betweenthe motor and the hammer is so constructed that the motor will rotatethe hammer and anvil so long as the work resistance is insuilicient toovercome the driving torque. However, when the torsion set up bythe workis greater than the driving torque and sufiicient to prevent movement ofthe anvil by the hammer, this connection is designed to dis-` e'ngagethe hammer and the anvil.

While the hammer and the anvil are disengaging, theenergy supplied bythe motor is stored in a spring or accumulator device, and as soon asthese parts are completely disengaged the stored' energy is imparted tocause the hammer to reengage with and impact against the anvil jaws. v

Thus the stored energy is employed to impart an additional angularvelocity to the hammer over that imparted by the motor during the timethat the hammer and anvil are re-engaging and the kinetic energy of thehammer is transformed into work delivered to the anvil. A great manyforms of such connections have been proposed, but they' connection whichwill disengage the clutch member completely upon a slight angle ofrotation vof 5o the motor. y

It is still a further object to provide a device which is novel andwhich will overcome work resistance effectively and efiiciently.

A still further object is to provide a driving 55 connection which is ofrugged construction and not subject to excessive wear requiring frequentrepairs.

` These and further objects will be apparent from the followingdescription of which the drawing is a part.

In the drawing, similar reference numerals refer to similar parts.

Figure 1 is an elevational view in section of a device constructed inaccordance with the principles of the present invention, l

Figure 2 is a View in section taken along the line 2-2 of Figure 1,

Figure 3 is a view partly in section and partly in elevation of aportion of the device illustrated in Figure 1 showing the hammer andanvil disengaged, and

Figure 4 is a developed view of a portion of the device of Figure 1illustrating the parts in operating position.

Referring to Fig. 1 the rotary impact device is generally imndicated atI and consists of a casing 3 secured to the motor 5 by means of thebolts 1. The motor 5 may be any suitably controlled reversible motorhaving a shaft 9 rotating in the bearing I I. A iiange I3 is formed'onthe shaft 9 to prevent movement of the shaft 9 toward the motor.Thehexagonal portion I5 is formed on the shaft 9 in juxtaposition to thiiange I3. This hexagonal portion may, of course, be of any otherdesired construction so long as it will prevent relative rotation of therotary driving head I1 with respect to the shaft 9 and Will permit theshaft 9 to rotate the head I1 which is surrounded by a cup-shaped hammerI9 extending into the casing 3.

On the bottom of the cup-shaped hammer are clutch teeth 2| which areadapted to engagewith corresponding clutch teeth 23 mounted on the upperface of the anvil member 25. These clutch teeth 2| and 23 provide adisengageable driving means between the hammer member I9 and the anvilmember 25. 'I'he anvil 25 consists of a cylindrical portion 21surmounted by a ange 29 on the upper surface of which are mounted theclutch teeth 23. A bearing 3l situated within the tool may be secured tothe anvil, a shank 35,I

formed as an integral part of the anvil, extends from the cylindricalportion 21 of the anvil. The

wrench 33 is secured by any means, such as the set screw 31 to the shank35, and is provided with a socket 39 adapted to engage the nut 4| inorder that the nut may be secured to the bolt 43.

It is desirable that the hammer member I9 be maintained in axialalignment with the shaft 9 at all times, and for this reason anextension 45 is formed on the hexagonal portion I5 of the shaft 9. Thisextension is recessed in a guide rod 41 which passes through the bottomwall of the hammer I9 into a recess 49 formed in the upper part of theanvil member 25. Guide rod 41 acts as a spacer between drive head I1 andanvil 21 to hold the anvil down during disengagement of the clutch teeth2| and 23. cient diameter to permit rotation of the guide membertherein, and the guide member in turn permits free rotation of theextension 45 formed.

on the shaft I I.

Within the head I1, and surrounding the guide rod 41, is a thrustbearing 5| which permits the spring 53 to rotate with respect to thehead I'I. A spring 53 rests against the thrust bearing 5| at one endthereof, and the other end rests in a well 55 formed in the bottom wallof the hammer member I9. The purpose of the spring is normally to holdthe hammer clutch jaws 2| in engagement with the anvil clutch jaws 23,and to absorb and impart energy.v

The apparatus above described is an impact wrench of a conventionaldesign and the driving connection between the head I1 and the hammer I9will now be described.

On the side of the driving member I1, channels or races 51 are formed.These channels 51 are formed as shown in Figs. 3 and 4 with inclinedsurfaces 59'and 6| which meet at their lowermost point 63. Several ofthese doubly inclined channels are provided, and there is nointercommunication between the separate channels. The hammer member I9is provided with grooves 65 which are so placed that they cooperate withthe channels 51 formed on the driving head. 'Ihese grooves communicatewith openings 61 which extend through the wall of the hammerbmember I9and permit the insertion of the balls 13.

The arrangement of grooves 51 and 65 and ball members 13, which areguided in them, is to permit the hammer I9 to disengage the anvil member29 upon encountering a predetermined resistance thereof to rotation, andto assist in storing in the spring 53 energy which is subsequentlyexpended upon the anvil by the hammer.

Thus, when the torque of the shaft 9, transmitted through the jaws `2|and 23, is insuflicient to turn the anvil 29 due to the resistance ofnut 4|, the jaws 2| and 23 disengage by raising the hammer I9 againstthe compression of spring 53 during which the balls 13 roll up grooves51 and the grooves 55 correspondingly rise to lift the hammer I9. 'Assoon as the jaws 2| rise to the height of jaws 23 they slide on top ofthe latter until rotated to a point of complete disengagement therewith.Jaws 2I are then free of jaws 23 and spring 53 tends to extend itself.In so doing, the hammer |9 is forced to move much faster than the driver9 and because of this increased velocity, the kinetic energy thereof isincreased as the square ofl the velocity. As the The recess 49 is ofsuflispring 53 extends, the grooves 65 cause the balls 13 to rollpreferably almost down to the bottoms of the grooves 51 before the jaws2| and 23 reengage so that the jaws strike each other with the maximumpossible impact.

The arrangement above described provides the least possible friction incontacting parts. The bearing of balls 13 With the grooves 51 and 65 issubstantially without friction and in addition the balls 13, as theyroll, move a very slight distance in the grooves which enables thegrooves to be made relatively short. Actually, the grooves may be madeonly half the `length of cam surfaces previously used in similarapplications for impact Wrenches as is well known in the art. Thispermits the provision of a plurality of sets of grooves 51 and 65 togive suitable bearing and support for the hammer I9.

The number of jaws 2| or jaws 23 is optional. With two sets of suchjaws, two blows are delivered to the anvil 29 at each revolution whenthe nut 4| is being set.

It is understood that in setting nut 4| the hammering of the hammer I9upon anvil 29 continues as long as power is applied to shaft 9 and thatit is this hammering that causes the nut 4| to be turned to its seat. Avery important advantage of this wrench is `that the reaction upon thetool itself is negligible so that little effort is required by theoperator to prevent the casing from turning. This property is in a largemeasure due to the frictionless structure provided by this invention.

We claim:

1. In a rotary impact tool having an anvil and a hammer for striking theanvil, clutch members on the hammer and anvil, a spring to normally holdthe clutch members in engagement, driving means for the hammer, andmeans connecting the hammer and driving means comprising V-shapedchannels on the driving means having the arms of the V inclined at anangle to the horizontal substantially less than ninety degrees, invertedV-shaped grooves on the hammer member having arms at the same angle tothe horizontal as the arms of said channels, and ball members retainedin said V-shaped channels by said 'inverted V-shaped groove.

2. In a rotary impact tool having an anvil and a hammer for striking theanvil, disengageable cooperating clutch members on. the hammer andanvil, a spring to normally hold said clutch members in engagement,driving means for the hammer, and means whereby the driving means maydrive the hammer member when the clutch members are engaged and todisengage the clutch member when the driving means is incapable ofdriving the hammer member comprising V- shaped channels on the drivingmeans having the arms of the V inclined at an angle to the horizontalsubstantially less than ninety degrees, inverted V-shaped grooves on the-hammer having the arms of the V at the-same angle to the horizontal asthe armsy of said channels, and means guided by said channels andgrooves.

FRANCIS A. JIMERSON. HAROLD C. REYNOLDS.

